Ignitron, seal, and method of making



May 20, 1947- D. E. MARSHALL IGNITRON, SEAL, AND METHOD OF MAKING Filed Nov. 2, 1945 ....wiw

INVENTOR 0. .5. Maza/,941..

@WQ 1Q m VWL vATTORNEY Patented May 20, 1947 IGNI'I'RON, SEAL, AND METHOD OF MAKING Donald E. Marshall, Allwood, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 2, 1943 Serial No. 508,700

(Cl. Z50-27.5)

13 Claims. l

This invention relates to seals and methods of making the same, and more particularly to such for making a connection through the envelope of mercury-pool cathode devices for connection with the make-alive electrodes thereof.

The primary object of my invention, generally considered, is to provide an improved seal through the envelope of an ignitron for connection with the igniter thereof.

Another object of my invention is to provide an improved inlet lead for an ignitron which is adequately insulated from the mercury.

A further object of my invention is to avoid the necessity of cooling the insulation, which was formerly glass, through the lead to the ignlter of a mercury-pool cathode device.

A still further object of my invention is to provide a seal for ignitrons involving a combination of Koi/ar, ceramic and glass, whereby a stronger and better construction is produced.

An additional object of my invention is the production of a seal for ignitrons involving a ceramic or porcelain capable of withstanding thermal shock and matching the sealing glass in expansion characteristics, as well as the metal parts to which it is connected, whereby a construction mechanically strong and capable of withstanding a temperature of the order of 600 C. to '700 C. is obtained.

Other objects and advantages of the invention, relating to the particular arrangement and construction of the various parts, will become apparent as the description proceeds.

Referring to the drawings illustrating an embodiment of my invention approximately to scale and full size in the original drawings:

Fig. 1 is a vertical sectional View through an ignitron embodying my invention.

Fig. 2 is an exploded View of parts forming the seal for the make-alive electrode or igniter.

Fig. 3 is an elevational View of the assembled seal.

Fig. 4 is an axial sectional view of a modified seal, with the lead-in conductor structure including a terminal member in elevation.

The problem of making a connection through the vacuum envelope of a sealed ignitron to the make-alive electrode or igniter thereof has never been solved to entire satisfaction. It has been decided best to bring the leadin conductor I through the cathode header and the mercury pool. Thus it is necessary that the seal be vacuummtight and that the inlet head be adequately insulated from the mercury. It has been the practice to use glass in all Such cases. It has been recently discovered that the energy liberated by the igniter arc is capable of heating such glass to temperatures well in excess of 600 C. For this reason it has been necessary to cool the glass forming the seal by conduction through the metallic lead. Thus the glass insulation has had to be intimately sealed to the lead-in conductor, which is thus necessarily made of such material as Kovar or tungsten. This has resulted in constructions which are not strong and, therefore, subject to considerable breakage in manufacturing and subsequent handling,

In accordance with my invention, I form a good seal by using a combination of Kovar or other suitable seal metal, ceramic, and glass having a coefiicient of expansion matching that of the metal and the ceramic, With or Without steel. Two embodiments of my invention are illustrated in the drawings, the first one representing the use of a Kovar cap with a steel center lead, the alternative design representing the use of a Iovar rod sealed directly to a glass coating on a ceramic cylinder, I prefer the first design as requiring less exact expansion-matching of the various component materials, due to the greater possibility of iiexure of the Kovar cap, as compared with the Kovar rod.

I have found that the choice of the proper ceramic body is important. It must match Kovar sealing glass in expansion and be capable of withstanding a considerable amount of thermal shock. It must be mechanically strong and capable of withstanding temperatures ofthe order of 600 to '700 C. After trying a number of materials, I have found that the best are that designated as Stupakoff body #655, as manufactured by Stupakoi Laboratories, Inc., Latrobe, Pa., and that called B- by its manufacturer, Westinghouse Electric Corporation, East Pittsburgh, Pa.

Referring now to the drawings in detail, like parts being designated by like reference characters, and rst considering the embodiment of my invention illustrated in Figs. 1, 2 and 3, there is shown a rectifier I 0 of the type called an ignitron,

comprising a metal envelope or housing Il enclosing a mercury cathode I2, and a solid anode I3 insulated therefrom. The floor or bottom wall I4 of the ignitron has a power lead 20 and an opening l5 through which the lead-in conductor I6 to the make-alive electrode or igniter I1 extends.

In accordance with the present embodiment of my invention, I seal a preferably steel lead I6 through the opening l5 of they ignitron housing,

by taking a hollow ceramic cylinder I8, which the lead-in conductor I6 loosely iits, and coating or beading the normally-lower end portion thereof with glass i9. The glass I9 (which may be Corning #704) is ol such a composition that it satisfactorily seals with, not only to the ceramic or porcelain cylinder i3, but also the connecting metal part or parts, preferably formed of Kovar which, as is well known, is a patented alloy having the following composition: 28.7% to29.2% Ni, 17.3% to 17.8% Co, 52.9% to 53.4% Fe, not more than .06% C, not more than .5% Mn and not more than .2% Si.

I next take an eyelet 2|, of Kovar or other metal which seals satisfactorily to the glass used, comprising a hollow cylindrical portion22 and an outstanding annular flange 23 at its normallyupper end, and embeddingly seal the free edge of said cylindrical portion 22 into the normallyupper end portion of the glass coatingl'9,to produce the seal illustrated in Fig. l.

The lead-in conductor structure is completed byproviding the leacportiond at.its normally lower end, with` a head-or circular angeportion .24 and I weld, braze, or .otherwise securely electrically connect the lower or outer surface of this head to the inner surface of a cup 25, of Kovar orother metal which-seals satisfactorily'to Ythe glass used.

froth@ outer surface ofthe bottom wall 2G of thecup 25, Iweld'braze, or otherwise securely electrically connect a shortvpin 27, which pin desirably.correspondsin material and diameter with that ,of the lead-in conductor I5. To this pin I 4similarly secure an outer terminal contact mem- Aber128, which maybe `iormed of'any. desired conductive material, such as brass.

Theassembled lead-in conductor, cup, pin and terminal contact member =is then connected to theassembled glass coated ceramic I-B'and eyelet 2l, by inserting the upper or free end of the lead-in conductor [Sthrough the ceramic cylinder and embeddinglyfsealing the free edgev of the cup ,25 into the glass coating I9, to. produce the lead-in rassembly illustrated in Figi. The upper portions of the'assernbly are vthen inserted inthe aperture I'5,.as illustrated, and'theange 23 ofthe eyelet 2l welded, or otherwise 'suitablyconnected to the 'bottom wall iid. he igniter H, which may be of conventional form, is then secured to the upper portion of the lead-in conductor l to produce the complete .assembly illustrated in Fig. l.

lteferringnow to the embodiment of my inventionillustrated in Fig. 4, there is shown a construction'somewhat similar to that of Figs. .1. to 3, inclusive, in that the ceramic or porcelain cylinder 18a receives lead-in conductor la and has at itsilower end a terminal member 28a, said lead-,in .conductor being sealed to the ceramicA 18e, as well as theKovar eyelet ZIB, by rneans of a glass coating ISE.

.Howeven inthe present embodiment the glass coating is formedas a relatively large bead in which the ends of both the cylinder lfl'and eyelet 2FL are embedded. Theilead-in conductor Iia, is necessarily formed of Kovan or some other material matching the glass lee, as the seal with said glass is relied upon in making a vacuumtight assembly. `r-Ehis makes it undesirable to make the lead-in conductor a of steel, as was done in the preceding embodiment. As in said precedinf7 embodiment, however, the Kovar eyelet 2in may be similarly formed with la ange 23a for connection with the lower wall of an ignitron envelope.

vthat modiiications may be made within the spirit and scope of theappended claims.

VI claim:

l. A seal comprising a hollow ceramic cylin- Vder with a glass coating fused on a portion of its exterior, a metal eyelet through which said .cylinderpasses and projects beyond both ends.

embeddedin one end of said coating, and having an outstanding flange for connection to the wall of a vessel, and a lead-in conductor passing through said cylinder and sealed thereto by vmeans of said coating.

2. A sealfcomprising a hollow ceramic cylinder with a glass 'coating fused'on a portion of its exterior, a metal eyelet through which said cylinder passes, embedded into one end of said coating, and having an outstanding flange for connection to the wall of a vessel through which said cylinder passes, a lead-in conductor passing through said cylinder, and a metal cap to the inner surface of which the outer end of said leadin conductor is secured, said cap having its edge fused into the adjacent end of said glass coating to complete the connection to said cylinder.

3. A seal comprising a hollow ceramic cylinder with a glass coating fused on a portion of its exterior, a metal eyelet through which said cylinder passes, embedded into one end of said Coating, and having an outstanding flange for connection to the wall of a vessel through which said cylinder passes, and a lead-in conductor passing through said cylinder and said glass coating, the coating scaling said cylinder, eyelet and lead-in conductor adjacent one end of the cylinder.

4. A seal comprising a'hollow .i3-35 ceramic cylinder with a glass coating, of coeicient of expansion corresponding thereto and to Kovar, fused on a portion of its exterior, a Kovar eyelet through which said cylinder passes, embedded into one end of said coating, and having an outstanding Iiange for lconnection to the wall of a vessel through which said cylinder passes, and a lead-in conductor structure having one portion passing through said cylinder and another portion sealed thereto by means of said coating.

5. A seal comprising a hollow B-35 ceramic cylinder with a glass coating, of coeicient of expansion corresponding thereto and to Kovar, fused on a portion of its exterior, a Kovar eyeletthrough which said cylinder passes, embedded into one end of said coating, and having an outstanding Iiange for connection to the wall of a vessel through which said cylinder passes, a steel lead-in conductor `passing through said cylinder, and a Kovar cap to the inner surface of which the outer end of said lead-in conductor is secured, said cap having its edge fused into the adjacent end of said glass coating to complete the connection to said cylinder.

6. A seal comprising a hollow B-35 ceramic cylinder with a glass coating, of coefficient of expansion corresponding thereto and to Kovan fused on a portion of its exterior, a metal eyeode, a power lead extending from said bottomV wall, an igniter electrode dipping into said mercury, a lead structure connected to said igniter electrode and insulated from said bottom Ywall by means of a seal comprising a hollow ceramic cylinder with a glass coating fused on a portion of its exterior, and a metal eyelet through which said cylinder passes, embedded in one end of said coating, and having an outstanding flange con# nected in Vacuum-tight relationship with said envelope bottom wall, said last-mentioned lead structure having one portion passing through said bottom wall and cylinder, and another portion sealed to the latter by means of said coating.

8. An ignitron comprising a metal envelope, an electrode adapted to act as an anode suspended in and insulated from said envelope, a pool of mercury adapted to function as a cathode resting on the bottom Wall of said envelope, a power lead extending from said bottom wall, an igniter electrode dipping into said mercury, and a lead to said igniter electrode insulated from said bottom wall by means of a seal comprising a hollow ceramic cylinder with a glass coating fused on a portion of its exterior, a metal eyelet through which said cylinder passes, embedded into one end of said coating, and having an outstanding flange connected in vacuum-tight relationship with said envelope bottom wall, said last-mentioned lead passing through said bottom wall and cylinder, and a metal cap to the inner surface of which the outer end of said lead-in conductor is secured, said cap having its edge fused into the adjacent end of said glass coating to complete the connection to said cylinder.

9. An ignitron comprising a metal envelope, an electrode adapted to function as an anode suspended in and insulated from said envelope, a pool of mercury resting on the bottom wall of said envelope and adapted to function as a cathode, a power lead extending from said bottom wall, an igniter electrode dipping into said mercury, and a lead structure connected to said igniter electrode and insulated from said bottom wall by means of a seal comprising a hollow ceramic cylinder with a glass coating fused on a portion of its exterior, and a metal eyelet through whiich said cylinder passes, embedded into one end of said coating, and having an outstanding flange connected in vacuum-tight relationship with the envelope bottom wall, said last-mentioned lead structure having one portion passing through said cylinder and glass coating, the coating sealing said cylinder, eyelet and another portion of said lead structure adjacent one end of the cylinder.

10. The method of making a seal, comprising coating the exterior of one end portion of a hol- 10W ceramic cylinder with glass, placing a metal eyelet over the other end of said cylinder and fusing the adjacent edge portion into said glass coating, passing one portion of a lead-in conductor through said cylinder, and sealing another portion of said structure thereto by means of the other end portion of said coating.

11. The method of making a seal comprising coating the exterior of one end portion of a hollow ceramic cylinder with glass, placing a meta-l eyelet over the other end cf said cylinder` and fusing the adjacent edge portion into said glass coating, sealing a metal cap to one end portion of a lead-in conductor, passing the other end portion of said conductor through said cylinder, and sealing the edge of said cap into the adjacent end of said glass coating to complete the connection to said cylinder.

l2. The method of making a seal comprising coating the exterior of one end portion of a hollow ceramic cylinder with glass, embedding one end of a metal eyelet through which said cylinder passes into the end of said coating adjacent the uncoated portion of said cylinder, and passing a lead-in conductor through said cylinder and glass coating so that the latter effects a seal between the conductor, eyelet, and cylinder.

13. An ignitron comprising a metal envelope, an electrode adapted to function as an anode suspended in and insulated from said envelope, a pool of mercury supported by the bottom wall of said envelope to function as a cathode, a power lead extending from said bottom wall, an igniter electrode dipping into said mercury, and a lead structure for said igniter electrode insulated from said bottom wall by means of a seal comprising a hollow ceramic cylinder extending from below said bottom wall to above said mercury, with a relatively-thick glass coating fused on a portion only of its exterior near its lower end, a metal eyelet through which said cylinder loosely passes, the lower end of said eyelet being eme beddedly sealed into the upper end portion of said coating and having an outstanding flange con nected in vacuum-tight relation with the envelope bottom wall, said lead structure having one portion passing through said cylinder and the lower portion of the glass coating thereon embeddedly sealing another portion of said lead to said cylinder adjacent the lower end of the latter.

DONALD E. MARSHALL.

REFERENCES CITED The following references are of record in the le of this patent:

UNTED STATES PATENTS Number Name Date 2,147,417 Bahls Feb. 14, 1939 2,217,398 Baier Oct. 8, 1940 2,241,505 Cuttler May 13, 1941 2,339,499 Marshall Jan. 18, 1944 2,306,808 Hutchings V- Dec. 29, 1942 FOREIGN PATENTS Number Country Date v 850,831 France Sept. 18, 1939 

